Sending 'rats' to Mars

NASA and JPL are sending "rats" to Mars to work as field geologists. A "rat" is not quite a furry little friend, but rather a high-tech robot with diamond teeth, called a rock abrasion tool.

One rock abrasion tool will ride on each of the twin Mars Exploration Rovers, launching in the summer of 2003. These tools will allow humans to remotely "crack open" rocks on Mars for the first time in the history of Mars exploration.

"This is terribly exciting, but it's a little intimidating because no one has ever tried to get into a rock on Mars before," says Stephen Gorevan. Gorevan is the chairman of Honeybee, the small robotics contractor for the rock abrasion tool located in New York City. Gorevan explains that past missions to the martian surface had different science and technology objectives. " The Viking landers in the 1970's scooped up dirt on Mars and the Sojourner rover proved we could move around on Mars in 1997." Digging into a rock is the next step for the maturing Mars program.

Bringing a rock back from Mars or sending a human geologist comes with prohibitive costs, so sending the rock abrasion tool is the next best thing. The tool will enable scientists to peer inside a rock, where they can analyze unweathered minerals and learn about the origins of rocks. Rick Paynter, deputy lead for Quality Assurance on the Mars Exploration Rover project at NASA's Jet Propulsion Laboratory, explains that the tool will help "peel off the orange rind" and reveal new information about the evolution of Mars. It will also help with comparing rocks on Mars to rocks on Earth.

How the Rat Runs

The Mars Exploration Rover will traverse Mars, find a rock that's interesting, nuzzle up to it, and maneuver its robotic arm to press the rock abrasion tool up against the chosen rock. The abrasion tool, which is the size of a soda can, will shave away the top layers of the rock. That process may take anywhere from 30 minutes to three hours to remove a round hole about 45 millimeters (1.5 inches) in diameter and 5 millimeters (1/8th inch) deep, depending on the texture of the rock.

It's more like an electric shaver than a drill, says Steve Kondos, contract technical manager at JPL . "The difference is, the shaver heads move in and out rather than being stationary - this takes less power. Power, energy, and mass are precious on the rover, so in order to be efficient, we shave the rock rather than drill it, which is power intensive."

After the tool shaves off part of a rock, it scurries aside via a Dr. Seuss-like arm device, which also holds a camera and chemical analysis tools to explore the newly exposed rock layers. Before it goes to grind another rock, it turns around and brushes its "teeth" against a brush spins against it to clear out leftover rock. The RAT is designed to grind away one rock, but could shave up to as many as 10 rocks.

The Rock Abrasion Tool is the brainchild of Mars Exploration Rover Principal Investigator , Steve Squyres of Cornell University, Ithaca, NY. Gorevan of Honeybee says, "Squyres thought of the need to expose a rock on Mars, and got us from point A to point B. Our job has been to get from point B to point Z."

After winning the competitive instrument contract, the Honeybee team has had to follow strict size, mass and pressure requirements generally dictated by the strength limitations set by the robotic arm. The Honeybee team had to use its ingenuity to come up with the optimum way to provide a mini crater in a martian rock. Gorevan says, "We cobbled and cogitated together to test ideas, and we're at about point W on the way to Z."

The Rats in New York now have Motors

Last week, Steve Kondos and Rick Paynter from JPL hand-delivered to Honeybee the motors that run the tools. "We're really conservative at JPL. The value of the instrument far exceeds the cost," says Paynter. "We split the motors and carried them in different pieces of luggage and took separate planes to New York City."

Now that JPL delivered the motors, "we have a clear path to finish our environmental tests and 'shake and bake' the tool." "Shake and bake" is a process used by engineers to ensure that instruments can withstand the intense vibrations and heat of launch, the extraordinary impact of landing on Mars, and the strong radiation exposure during interplanetary cruise. As time races toward launch, other challenges still remain. "One surprise has been to find how much dust is created by the rock abrasion tool," explains Gorevan at Honeybee. As the robot grinds away at a rock, it generates dust plumes that can blow onto the solar arrays of the rovers or the cameras."

Steve Kondos from JPL calls the people at Honeybee ingenious. "They are concerned with cost and schedule milestones, and best of all, they are fun to be with. Since we come from LA, the Honeybee team introduces us to little known spots, like a deli where the bread is so good that Frank Sinatra used to have loaves shipped from Manhattan to Hollywood every week."

New York, 9/11, and Mars

"After September 11 happened, the first thought was how the team at Honeybee was affected, explains Kondos. "We called immediately, but of course couldn't get in contact with them." Luckily, no one on the team was hurt.

NASA Headquarters just approved putting an American flag on the rock shield of the rock abrasion tool. "It's not the equivalent of placing the American flag in the rubble pile, but it's something like that." Kondos is quiet for a moment, then adds, "We're not stopping our progress and hiding, we're rising to the stars."